Crank Bearing.

[Glyn.G]

Hi All,
I've been rebuilding a GT380 engine and I'm now at the stage of sending the crank away to be rebuilt by SEP Kegworth. The problem I have is the original crank I took out was too badly damaged to reuse so I purchased a second used crank. All was going well until I did a quick double check on the crank again before I sent it off. It all looked fine as I was told it came out of a running bike but the seals were suspect. The big ends were fine and no visible damage then I checked the mains.
One of the plain centre bearings ( no groove ) actually slides from side to side on the shaft. By this I mean the inner race does not seem to be a press fit, all the rest are nice and tight. I can see or feel no damage to the shaft and there is no sign it has been overheating ( no colour change to bearing ).
This has me baffled. Any Ideas or shall I try and find yet another crank.
Regards,
Glyn.

[Alan H]

Let Sep sort it.
Tell them to use genuine rods, seals and bearings.

[Glyn.G]

Hi again,
Can anyone tell me if there is any difference between 1972-1977 Gt380 crankshafts.
Regards,
Glyn.

[Alan H]

J/K, L, AND M/A have different part numbers, but what the differences actually are is anyone's guess.

[Glyn.G]

I now have a fully remanufactured crank on the way and I have a couple of questions that could do with your input.
Firstly, has anyone got any preferences as to which crankcase sealant I should use when putting the cases together. Secondly I was wondering whether to fit the oil seals ie Clutch pushrod seal, Final drive shaft, and Kick start shaft blanking rubber before or after I bolt up the 2 halves. I know the outer crank seals need to be in place prior to bolting together but not sure about the rest.

[tz375]

I use Three Bond.

Fit all the seals in place before you close the cases so that they are compressed in place. The OD of a seal is slightly larger that the hole it fits into and bashing it in when the cases are closed is not a good idea except in an emergency.

[Glyn.G]

I use Three Bond.

Fit all the seals in place before you close the cases so that they are compressed in place. The OD of a seal is slightly larger that the hole it fits into and bashing it in when the cases are closed is not a good idea except in an emergency.

Thanks tz375,
There seem to be a lot of different numbered tubes of Three Bond on the market and all seem to do the same job," I'm confused ".
Just a small ask. If I'm not going to be using the rebuilt engine straight away should I do anything to prevent the new seals from drying out, especially the crank seals.

[Zunspec4]

Hello Glyn,

Threebond 1104 is the type I use for joining crankcases. I apply thinly and evenly to one case only using a small paint brush.

Cheers Geoff

[jabcb]

Service bulletin General-16 says to apply the sealant to only the top crankcase half & then wait 10 minutes.
Is that the typical practice for ThreeBond?

http://www.ozebook.com/compendium/techb ... 010-18.pdf

[Glyn.G]

Hello Glyn,

Threebond 1104 is the type I use for joining crankcases. I apply thinly and evenly to one case only using a small paint brush.

Cheers Geoff

Cheers Geoff, I'll get some ordered.

[ConnerVT]

Service bulletin General-16 says to apply the sealant to only the top crankcase half & then wait 10 minutes.
Is that the typical practice for ThreeBond?

It says to apply a "thin layer". After you have done it once, you will understand that thin is *really* thin.

Ideally, the two case halves are perfectly precision machined, such that there would be no leaks at all. The sealant just needs to fill the tiniest of gaps, squeezing the remaining sealant out, both outside and inside the casings. Easy enough to clean up on the outside, but makes you worry what's going on inside the crankcase.